This invention relates to chucks for machine tools designed either for high-speed operation or machining operations in which the chuck must sustain severe lateral forces due to the machining pressures exerted on the workpiece. In either case, it is essential that the workpiece be positively held and that the grip on the workpiece is capable of positively resisting any forces, such as centrifugal forces, which would tend to cause it to loosen its grip on the workpiece. This latter requirement has become much more urgent and meaningful as both the operating speed and the pressure exerted by the tools on the workpieces have been increased.
The problem has been to satisfy the need for better and more positive engagement with the workpiece without materially increasing the cost of the chuck or limiting its utility.
Heretofore chucks designed for the service conditions to which this invention is designed to be applied have been limited to a very small jaw movement capability. As a result, the chucks have a highly specialized and limited use and are not adaptable to use with workpieces of any significant range of dimensional difference without a long and complicated rework adjustment of the chuck. Since such chuck adaptation work must be done by skilled personnel, the cost of adaptation of the chuck from one job to another has been prohibitive unless the length of the run on which the chuck is to be used is of sufficient size that the cost of adaptation can be absorbed.
This invention overcomes this difficulty by providing means by which such chucks can be quickly adapted to serve a much wider range of workpiece sizes with a minimum downtime requirement and without the necessity for use of highly skilled labor to perform the changeover. In fact, with this invention, the changeover can be made be so rapidly that there is no reason to attempt to use the machine on which the chuck has been mounted for any other purpose while the changeover is being made. Further, this permits the chuck to be used for a much wider range of work and, thus, for a much higher proportion of its availability. Thus, its cost can be amortized over a much larger proportion of availability time. Further, it reduces the number of chucks which a firm must have on hand in order to profitably machine a wide range of jobs. It reduces the amount of machine tool downtime necessary for changeover from one job to another. Since each chuck can be used over a much wider range of jobs, the necessity for providing storage space for chucks not currently in use is significantly reduced. Overall it significantly increases the scope of the jobs a machine shop can profitably perform on each of its chucks. Thus, the chuck's return on capital is materially increased and the amount of storage space required for idle chucks is significantly reduced.